Mobile electronic devices, such as radios and cellular telephones, typically rely on power from one or more internal batteries. A major performance criterion for such devices is the battery life, which is typically defined as the time period for which the battery will power the device on a single charge. A large portion of the battery power is consumed in a power amplifier (PA) section of the mobile electronic device's transmitter. The power amplifier section amplifies the power of a signal to be transmitted from a comparatively low internal power level to a substantially higher power level required for wireless communication with remote base stations or other devices.
Power efficiency is even more important with multimedia services that consume significantly more power than traditional voice communication services. Thus, improving the power amplifier efficiency or, more generally, transmitter efficiency, is an important factor in battery life performance.
One of the main difficulties in extending battery life is related to the modulation schemes now being used. Modulation methods such as code division multiple access (CDMA), orthogonal frequency division multiplexing (OFDM), and other types of multi-carrier modulations exhibit high peak-to-average power ratios (PAPR). Further complicating the problem is the stochastic nature of the required transmitter power. These transmitters are required to provide both large dynamic range and good linearity. In addition, some standards require quick variation in both output power and PAPR. For example, air interface standard CDMA2000 requires provisioning for variations of up to 800 dB per second.
Current transmitters are designed for peak power utilization. Thus, at low power utilization, the power efficiency is lower than at peak power utilization. There is a resulting need in the art for a way to optimize transmitter power efficiency.